As a conventional ball screw device, there has been disclosed a ball screw device which is described in Patent Document 1. The ball screw device disclosed in Patent Document 1 is disposed so as to divide a resin circulating part (not shown) into two, and to substantially match (substantially match with a tangential direction of spiral path) with a centerline of the circulating route in a circulation route in a leg of the circulating part fit into a circulation hole of a nut with a tangential direction and with a lead angle direction of both screw grooves, to realize smooth scooping of a ball (rolling element).
However, the ball screw device disclosed in Patent Document 1, there is fear that because the circular part is divided into two in a radial direction along a centerline of a ball circulation route, which might fall into a situation where a tang for scoping up the ball is also divided, which might induce deterioration of strength of the tang.
To avoid the deterioration of the strength due to such division of the tang, there has been disclosed the ball screw device as disclosed in Patent Document 2.
FIG. 5 is a perspective view showing a divided body of the circulating part of the conventional ball screw device described in Patent Document 2. FIG. 5A is a perspective view viewing the divided body from one direction. FIG. 5B is a perspective view viewing the divided body from the other direction opposite to that shown in FIG. 5A.
As shown in FIGS. 5A and 5B, the circulating part 140 of the ball screw device disclosed in Patent Document 2 is composed of two divided bodies 140a,140a point symmetrically divided into two along a route direction of the ball circulation route R. That is, the two divided bodies 140a,140a are coupled with each other at divided surfaces A,B,C on which a circular groove 143 is formed for constructing the ball circulating route R, for constructing the circulating part 140. Each divided body 140a,140a respectively have a pair of legs 141,141 and a body 142 to connect the pair of legs 141,141.
These pair of legs 141,141 are fit into a pair of circular holes (not shown) drilled in a direction substantially orthogonal to an axle line of a nut in the ball screw device, so as to communicate with a spiral path formed by a screw groove of a screw shaft and a screw groove of the nut of the ball screw device. At an end of one leg 141 out of the pair of the legs 141,141 of the divided body 140a, a tang 144 is provided to scoop up a ball rolling in the spiral path K in a direction substantially match with a tangential direction of the spiral path. Further, at an end of the other leg 141 (the leg 141 at which the tang 144 is not provided) out of the pair of the lags 141,141 of the divided body 140a, a relief 145 is provided to prevent contact with a screw shaft (not shown).
Patent Document 1: U.S. Pat. No. 2,851,897 A
Patent Document 2: JP 2006-125578 A